The invention relates to exposure systems, and more specifically to the use of two dimensional light modulators, also known as light valves, in exposure systems. When large area light valves are used it is difficult to uniformly illuminate all cells of the light valve. This will cause non-uniform exposure when the light valve is imaged onto an imaging surface. A second problem with large light valves is the high probability of defect, caused either by dirt or a defective cell. As the number of cells in the light valve increases so does the probability of having a faulty cell either during manufacturing of the light valve or due to failure during use. The present invention is particularly useful in conjunction with the exposure method disclosed in U.S. Pat. No. 5,049,901. It can be used with any form of light valve but is particularly useful with Deformable Mirror modulators, manufactured by Texas Instruments Inc (Texas). The principle of operation of the Deformable Mirror modulators is covered by U.S. Pat. No. 4,441,791.
Current use of light valves calls for defect free operation and a high degree of light uniformity. Both these requirements significantly increase the cost as well as limit the usefulness of light valves.